Features

• No Current Sense Resistors Required
• Out-of-Phase Controllers Reduce Required Input Capacitance
• Tracking Function
• Wide V_IN Range: 2.75V to 9.8V
• Constant Frequency Current Mode Operation
• 0.6V ±1.5% Voltage Reference
• Low Dropout Operation: 100% Duty Cycle
• True PLL for Frequency Locking or Adjustment
• Selectable Burst Mode®/Forced Continuous Operation
• Auxiliary Winding Regulation
• Internal Soft-Start Circuitry
• Power Good Output Voltage Monitor
• Output Overvoltage Protection
• Micropower Shutdown: I_Q = 9µA
• Tiny Low Profile (4mm × 4mm) QFN and Narrow SSOP Packages

Typical Application

Description

The LTC3736 is a 2-phase dual synchronous step-down switching regulator controller with tracking that drives external complementary power MOSFETs using few external components. The constant frequency current mode architecture with MOSFET V_DS sensing eliminates the need for sense resistors and improves efficiency. Power loss and noise due to the ESR of the input capacitance are minimized by operating the two controllers out of phase.

Burst Mode operation provides high efficiency at light loads. 100% duty cycle capability provides low dropout operation, extending operating time in battery-powered systems.

The switching frequency can be programmed up to 750kHz, allowing the use of small surface mount inductors and capacitors. For noise sensitive applications, the LTC3736 switching frequency can be externally synchronized from 250kHz to 850kHz. Burst Mode operation is inhibited during synchronization or when the SYNC/FCB pin is pulled low in order to reduce noise and RF interference. Automatic softstart is internally controlled.

The LTC3736 is available in the tiny thermally enhanced
(4mm × 4mm) QFN package or 24-lead SSOP narrow package.

Protected by U.S. Patents including 5481178, 5929620, 6144194, 6580258, 6304066, 6611131, 6498466.